To provide radio communications or signals from an undersea source, such as a submerged submarine, a radio antenna must be raised from that source to a position above the surface of the water to permit RF propagation into the overlying atmosphere. Communications buoys, carried in the submarine, serve in that function. As an example known to those skilled in this technology, a communication buoy may be released from a submerged submarine. The buoy conveniently floats to the surface carrying an antenna, and exposed the antenna to the atmosphere. Self contained RF equipment them transmits RF to a predesignated frequency carrying modulated with information to other radio stations listening on the transmitting frequency.
In Arctic regions, moreover, one is confronted with polar ice overlying the sea. The ice is a physical barrier to movement of any buoyant object from the under side and, like water, does not adequately propagate RF energy. For Arctic environments, thus, the communications buoy, more aptly referred to as the Arctic communications buoy, includes a penetrator for penetrating the ice and creating a passage through which an RF antenna may be raised from beneath the ice.
One type of ice penetrator that has gained acceptance in that application is of the thermochemical type. The ice penetrator uses heat generated by a thermochemical reaction between material of the penetrator and the ice to melt a hole through the ice. One reactant is water, which is at least partially supplied by the ice as it melts. The second reactant is the thermochemical material of the penetrator which reacts exothermally on contact with water. Such penetrator material is, typically, an alkali metal or an alloy containing a alkali metal, preferably lithium. The reaction products include lithium hydroxide, a solid that may dissolve in water, and hydrogen, a gas. The reaction products are pertinent to aspects of the present invention.
An excellent source of more detailed background of, structure to and applications for the present invention is found in the patent to Eninger, et. al., U.S. Pat. No. 4,651,834, granted Mar. 24, 1987, assigned to TRW Inc, the assignee of the improved ice penetrator herein described and this application. To avoid unnecessary repetition herein one should make reference to the Eninger, et. al. patent as that background information is incorporated by reference in this specification.
As may be noted in the Eninger Patent the geometry of the outer surface of the penetrator's front end therein illustrated possess somewhat flat or blunt shapes. Later designs for ice penetrators produced in accordance with the Eninger patent, however, are artillery shell shaped or, as alternatively viewed, bullet shaped in geometry, a shape which appears to enhance the penetrator's speed of penetration through ice without undue consumption of the penetrator's material.
Although successfully applied, it has been discovered that under certain circumstances the lithium penetrator has a serious drawback. If released from a depth of between 300 and 600 feet under the water surface, the penetrator produces an acoustic report, a somewhat loud explosion, on contact with the water. When used in military submarines such noise could alert enemy vessels to the submarine's presence with possible calamitous results. Importantly, should the explosion occur too close to the submarine damage to personnel and equipment could possibly result. The present invention eliminates that hazard. Moreover, should the compartment housing the penetrator, the buoy table, inadvertently become flooded with water while in a deeply submerged submarine, at the high pressure existing at such depths one conceives that a similar potential for damage could result. The present invention also eliminates that potential hazard.
The mechanics of the explosive reaction are not fully understood. It is believed, however, that at the high pressures existing at great ocean depths, the lithium penetrator generates more heat than it can safely dissipate in the water, eventually melting the lithium and/or causing the penetrator to break apart into many smaller pieces. As is known, lithium is more reactive in the molten state. A greater surface area of highly reactive lithium is thus exposed to the ocean water in a relatively short period of time, resulting in the very violent chemical reaction, an explosion. Should the penetrator include sodium, which is even more reactive in water than lithium alone, more intense reactions might occur.
An object of the present invention therefore is to prevent thermochemical ice penetrators from exploding when exposed to the ocean water at great depths;
An additional object of the invention is to provide an improved ice penetration apparatus that cannot cause acoustic reports;
A further object of the invention is to provide a safety mechanism for strong and handling lithium type ice penetrators or ice penetrators containing other more reactive metals, such as sodium, that are alloyed with lithium; and
An additional object is to prevent undue fragmentation or melting of the ice penetrator before and during deployment.